Thousands of young people from elementary to collegiate level participated in demonstrations one month after a gunman killed 17 people at Marjory Stoneman Douglas High School. Parents, teachers and allies also joined in.

Together, they honored those who lost their lives in mass shootings and demanded that Congress pass stricter gun legislation.

Washington, D.C.

Teenagers started the day holding up the names of the 17 Parkland victims outside the White House.

Nevada

Alan Cruz, a young activist from Canyon Springs High School in North Las Vegas photographed this powerful moment from the walkout.

“I joined the protest first as a student who cares about my own safety and safety of the school because we deserve to go to school without worrying if we’ll get shot,” he said. “Being shot isn’t on my to-do list to graduate.”

Cruz stressed the importance of listening to how students of color and disabled students feel about gun violence. He suggested an “intersectional” approach to school safety that considers the needs of everyone.

New York

Libi Ariel, a 12-year-old student at Hannah Senesh Community Day School, made a clear case during a rally in Brooklyn.

Colorado

Molly Reynolds, an education major at University of Colorado Boulder, also disagreed with the idea that arming teachers could solve gun violence. So she turned to civic engagement as a means to make a difference.

“Vote out politicians who take NRA blood money. Vote out politicians who believe that the safety of weapons is more important than the safety of children,” she wrote on Instagram. “Enough is enough.”

The big message

Overall, the young people who chose to walk out of school on Wednesday shared one resonating theme: They are the next generation of leaders, and they deserve to be heard.

(CNN) — In an unprecedented show of unity and political solidarity, waves of students marched out of class Wednesday to demand stricter gun laws and an end to school massacres.

The National School Walkout started at 10 a.m. ET and will continue across the country at 10 a.m. in each time zone. The protest was sparked by last month’s school massacre in Florida and fueled by years of anger about what many say are inadequate gun laws.

“This is not a matter of left versus right. This is a matter of public safety,” said Cate Whitman, a junior at LaGuardia High School in New York. “We’re all working together, which is something we haven’t seen from the adults in a very long time.”

In New York, students warned lawmakers that they are the future — and will soon be old enough to vote officials out of office if they don’t pass tougher laws.

“We are the change!” they chanted.

Walkout goes global

From Israel to Tanzania, students across the globe also left their classrooms Wednesday in solidarity with the American students’ movement. In some places, students talked with teachers about “how lucky they are” that guns aren’t a part of their everyday lives.

Eduard Štrébl, a senior at Walworth Barbour American International School in Israel, organized the walkout on his campus.

“I’m from Prague, Czech (Republic), and I’m not American,” he said. “But to see an epidemic of school shootings in a developed country when it’s so easy to limit such things, to see that there is nothing being done against that, that inspired me to organize the walkout here.”

Why some students disagree

Some students chose not to walk out with their classmates — and for different reasons.

Austin Roth, a senior at Lapeer High School in Michigan, said he’s “100% supportive of those who choose to be in the national walkout to show they care about the lives lost in Florida and every other school shooting.”

“However, I am not supportive of those who use a tragic event to push their political agendas, such as gun control,” he said.

Instead of walking out, Austin and other young Republicans from his school gathered in the cafeteria to voice their opinions.

Austin, 17, says he’s a “staunch Republican” who carries a copy of the Constitution in his pocket.

“I do support federal background checks, (and) I’m not completely against raising the age to 21” to buy firearms, Austin said.

But he said he strongly disagrees with the notion of banning assault rifles, saying they can be useful when confronted with multiple burglars or other criminals.

“Guns are not the problem. The people are the problem,” Austin said.

In Minnesota, 16-year-old Noah Borba said he didn’t walk out because he doesn’t fully support the movement.

“Because I have yet to have heard many good ideas, the movement seems too vague for my liking, and I would not like to associate myself with something I could end up disagreeing with in the future,” said the Buffalo High School sophomore.

While it would be “pretty cool” if the country banned assault rifles, “I don’t think logistically it’s realistic” to get rid of all the assault rifles already out there, Noah said.

Not just about school massacres

Organizers from the Women’s March youth branch called for students across the US to walk out of class on March 14, to pressure lawmakers to act on gun control. In addition to walkouts, students across the country planned rallies, marches and sit-ins — some in open defiance of their school districts.

Participants said they want to make sure calls for change in the wake of the mass shooting in Parkland, Florida, take into account the full context of gun violence in the United States.

For D’Angelo McDade, a senior at North Lawndale College Prep High School in Chicago, gun violence is personal — but not because of a shooting at school.

He was shot in the thigh as he sat on his front porch last summer, leaving bullet fragments in his body, he said. So, D’Angelo took the lead in organizing his school’s walkout Wednesday.

“Many of our community members and young adults have established a sense of hopelessness and normalized the suffering that comes with gun violence,” he said. “But they’re ready to see a change.”

Penalties for walking out

Some school districts have said they will discipline students who participate in the walkouts.

Students who leave classes in New Richmond, Ohio, for instance, will receive an “unexcused tardy,” the district said. For students in Montgomery County, Maryland, walking out will count as an unexcused absence.

In the Atlanta suburb of Cobb County, Georgia, the school district said it will take disciplinary action — ranging from Saturday school to five days’ suspension, per district guidelines — against students who walk out, citing safety concerns.

The prospect deterred some students, but not all of them, Pope High School senior Kara Litwin said.

“Change never happens without backlash,” she said Tuesday. “This is a movement, this is not simply a moment, and this is only the first step in our long process.”

Outside Walton High School in Cobb County, some parents stood Wednesday morning with signs reading, “Children Over Guns” and “We Demand Action!”

Growing up in the shadow of gun violence

Students who planned to participate in the walkouts said they feel their generation has been profoundly shaped by the specter of gun violence. By raising their voices, they hoped they will be the last kids to grow up with metal detectors and active shooter drills.

Sam Craig of Littleton, Colorado, was born after the 1999 Columbine High School shooting that put his hometown on the map. But the tragedy shaped his life.

He grew up with school lockdown drills undertaken in the name of Columbine. His internship at the Denver Zoo includes live shooter drills and references to Columbine. He knows a teacher who was at Columbine during the shooting and openly shares his view that school staff should not be armed, Sam said.

But the Chatfield High School junior said the community is stronger because of the shooting. People look out for each other because they don’t want anyone to feel “pushed to the point of no return” like the Columbine shooters, he said.

Each year, the town comes together on the anniversary for a day of service, he said.

“We try to find that balance to make our community more connected and loving,” said Sam, who is organizing the walkout at his school.

Abigail Orton, a junior at Columbine High School, said she was inspired to take action on Wednesday by the quick progress of the Parkland students.

“I am absolutely amazed at the amount that they’ve already accomplished, getting their voices out there and being able to speak on this so recently after the event, and to be able to use their status to start bringing about change,” she said.

“I’m honored to be able to call this my generation and to be part of this movement.”

Scenes too familiar

Jackson Mittleman was 11 and in sixth grade when a gunman killed 20 first-graders and six educators at Sandy Hook Elementary, two miles from his school. The tragedy changed the course of his life.

Now 16, he’s a gun control advocate who supported Wednesday’s school walkout.

“A message we’re trying to send to Parkland is we stand behind them,” said Jackson, co-chair of the Jr. Newtown Action Alliance, who organized the walkout at Newtown High School. “We are motivated, and we are fired up to push as hard as they push and fight as long as they fight.”

When Mittleman opened a news alert on his phone on Valentine’s Day and saw students with their hands raised, fleeing a shooting, his heart ached for the students of Marjory Stoneman Douglas High.

He saw yet another community joining what he calls a family “no one wants to be a part of.”

He asked himself, “Is it ever going to stop?”

Tanzania

At the International School of Tanganyika in Dar es Salaam, Tanzania, students and teachers used the walkout as an opportunity to talk about gun violence and US politics.

“We are lucky to live in a country that is relatively (civilian) gun-free, so it’s not something our students have to think about,” said Courtney Park, a teacher and librarian. “But they are aware of the school shootings in the USA, and some understand the greater contexts of the NRA and its influence in politics.”

Some conversations included students’ sense of “how lucky they are” that guns aren’t a part of their everyday lives, Park said, noting that about a dozen of the school’s teachers, plus the principal, are American.

Another teacher wanted to send the message to students and teachers in Parkland, Florida — where a massacre a month ago sparked the walkout movement — that they are not alone.

“This is not a problem in one school with a limited effect, said Pinckney Steiner, who teaches science. “The conversation is international and includes people of many nationalities. My hope is that the governors of all states, the representatives and senators from all states will listen to us and know that change is needed. The world is listening.”

Israel

The walkout at Walworth Barbour American International School in Even Yehuda, Israel, was organized by three students, including Eduard Štrébl.

“I was inspired to organize this walkout because I watched the movement get born online and it moved me. It touched me deeply to hear about this,” said Štrébl, a senior.

“I’m from Prague, Czech (Republic), and I’m not American, but to see an epidemic of school shootings in a developed country when it’s so easy to limit such things, to see that there is nothing being done against that, that inspired me to organize the walkout here,” he said.

Iceland

The walkout just happened to coincide with the International School of Iceland’s lessons on world events.

“This idea for us to participate in the walkout came recently during a current events discussion and a discussion on children’s rights around the world,” said Justin Shouse, who teaches fifth and sixth grades.

Students there also had been studying people younger than 25 who are changing the world. That now includes Emma Gonzalez, the Parkland shooting survivor who has become one of the faces of the #NeverAgain movement.

The Icelandic school’s protest did hit a snag, however. “If you are wondering why we are still in school, the Icelandic weather did not cooperate with the walkout today,” Shouse said, adding that it was cold, windy and raining.

Great Britain

Students at the American School in London congregated in a nearby park, held a banner and gave speeches during their walkout.

“The American School in London has not taken a position regarding the rationale behind the student-generated protest, but as always, we uphold our students’ right to a voice and an opinion, and commend their courage to act, their desire to effect change, and their efforts to make schools throughout the world safe places to learn,” Lydia Condon, the school’s communications coordinator, told CNN. “We believe this is a great opportunity for students to think about the power of their voices and their actions to bring about change in the world.”